Body and an electronic device

ABSTRACT

The body ( 10 ) comprises a first portion of transparent material and is provided with embedded optical and other elements ( 12, 13, 22, 16 ) and a pattern of conductors  15  used for interconnection and electrical contacting of the elements ( 12,13, 22,16 ). The first portion constitutes a light path from the optical elements ( 12 ) to either other opto-electronic elements or electro-optical elements embedded in the body ( 10 ) or present at a surface thereof. The electro-optical element is for instance a liquid-crystalline display ( 20 ) and the optical elements ( 12 ) are for instance light-emitting diodes, which are used for backlighting the display ( 20 ). The body ( 10 ) has a three-dimensional shape derived from its application and is preferably fitted for mechanical attachment of external components, that together constitute a device ( 100 ).

The invention relates to a body having a three-dimensional shape derivedfrom its application and comprising a first portion with a transparent,electrically insulating material constituting a light path to an opticalelement. The invention further relates to an electronic devicecomprising such a body and an optical element.

Such a body and such an electronic device are known as parts of mobilephones. Particularly, the body therein constitutes a light-guidestructure and the optical element is a light-emitting diode.Furthermore, a display is present. This known electronic device will befurther explained with reference to FIG. 1, which is a diagrammatic,perspective, exploded view.

The device 100 comprises a transparent body 10 acting as a light guideand as a mechanical support. A display 20 is attached to the body 10through a double sided tape 21. The display is, in this example, aliquid crystalline display and is provided with a glass surface to whichthere is attached an integrated circuit for addressing purposes, alsoknown as driver IC 22. Furthermore, there is provided a flexible printedcircuit board 1, to which various components are attached. At least twoof these components are the light-emitting diodes 12 (not shown), whichare provided with a lens. The display 20 and a connector 13 are alsoelectrically connected to the flexible printed circuit board 11. Throughthis connector 13 the display and the other components are provided withenergy and signals. The device 100 further comprises a loudspeaker 30, acasing 40, which is in this case a rubber overmolded bezel, as well asfoam tapes 27 to obtain the required mechanical stability. Further,there is provided a black sticker 23. The transparent body 10 isprovided with holes 18 and clamping means 19 for mechanical attachmentof the loudspeaker 30, the casing 40 and non-shown buttons.

It is a disadvantage of the known device that the resulting opticalperformance is not optimal. The presence of the light-emitting diodes 12on the flexible board 11 leads for instance to a relatively wide marginof tolerance in their directivity. This may lead to a backlighting ofthe display that is less uniform than desired.

It is therefore an object of the invention to provide a device of thekind mentioned in the opening paragraph having improved opticalperformance.

It is a further object to provide a body suitable for such a device.

The object relating to the body is achieved in that the body is providedwith a pattern of electrical conductors, and in said body at least oneoptical element is embedded, the optical element being electricallyconnected to the pattern of conductors, the pattern of conductors beingprovided with electrical connection means that are laterally displacedwith respect to the optical element.

The object relating to the device is achieved in that it comprises thebody of the invention and an opto-electrical or electro-optical elementattached to the surface of the body.

The invention is based on the insight that the optical element and theconductors that used to be present in a separate printed circuit boardare embedded in the body itself. This has substantial advantages withrespect to the optical performance. First of all, all relevantcomponents are attached directly to one and the same carrier, which isthe body. The margin of tolerance of the prior art, resulting from boththe attachment of components to a board and the attachment of the boardto the body, is thereby reduced. Secondly, the number of interfaces inthe light path between the optical element and the display is reduced.This results from the inclusion of the optical elements in the body.Furthermore, the design of the pattern of conductors may be optimized,such that the optical elements are positioned as favorably as possiblein relation to the display.

It is an advantage of the present invention that the mechanicalstability of the resulting device is good, which can be attributed tothe fact that the body serves as an encapsulation of components. As aresult of this function of encapsulation, the body may have a largerthickness without an increase of the dimensions of the device as awhole.

It is a further advantage of the present invention that the amount ofassembly is reduced. In fact, the assembly process is limited to a firststep in which the optical elements, and if so desired any furtherelectrical elements are provided on a carrier, and to a second step ofassembly of some larger elements at the surface of the body. After theprovision of the elements of the carrier, the body is provided using amolding technique, such as insert molding. Thereafter, a releasablelayer is removed from the foil and only the pattern of conductors isleft as part of the body.

It is another advantage that the present invention can be applied in amuch wider range of products than the device known from the prior art.The prior art device includes the combination of a light-emitting diodeand a display. Possible applications include optical transmission,optimized light output based on input of a sensor, optical discsincluding an integrated circuit for copy protection and a photodiode forenergy transfer to the integrated circuit; cameras; and modulescomprising optical and other functionalities.

From GB 2,229,864 a molded printed circuit board is known having adesired three-dimensional shape and being provided with a pattern ofelectrical conductors. Said document neither discloses that a firstportion of the material may be transparent, nor that any element may beembedded in the body. There is not any suggestion that the use of theproposed method of manufacturing may result in an improved opticalperformance of the device. Furthermore, it is not clear whether themolded board can have a support function and act as a structural elementin a device.

From EP-A 1,207,685 a chip scale package is known, in which a pattern ofconductors and an integrated circuit are embedded in one body. However,the body does not contain a portion of transparent material.Furthermore, the shape of this package is not derived from itsapplication but simply block-shaped. And the contact pads in the patternare not laterally displaced with respect to the electrical element.

The light path may be present between the optical element and anothercomponent in the body or at the surface of the body. Alternatively, itmay lead from the optical element to the surface of the body. The designof the light path thus depends on the application.

In a first embodiment, the light path is present between the opticalelement and a surface area of the body suitable for assembly of anopto-electrical or electro-optical element. Here the optical element andthe other element are optically interconnected. Particularly if theopto-electrical or electro-optical element includes an interface to auser, this location at the surface is preferable. An example hereof isthe combination of a liquid crystalline display and several diodes forbacklighting, the diodes being the embedded optical elements and thedisplay being the electro-optical element. Another example is a camerawith an electrically driven lens, for instance based on theelectro-wetting principle, and an image sensor. Generally, the lightpath between a lens and a sensor is realized with a through-hole.However, if the lens is completely embedded, the first portion may actas lens package and as light path, thereby removing the interface.

There are various ways of providing electrical contact between theconductors at the surface of the body and the electro-optical element atthe surface, particularly if the electro-optical element is aliquid-crystalline display. One option is the provision of a flexibleportion at an edge of the body, which can then be heat-sealed to thedisplay using an anisotropic conductive film pressed between theflexible portion and the display and cured with heat. The smalldisadvantage hereof is the additional process step for the provision ofa flexible portion. Another option is heat-sealing the body directly tothe display. In this case the electrically insulating material must beheat resistive. This limits the choice of the materials to rigidmaterials and sets further requirements to the allowed amount of surfaceroughness in the molding process. A third, preferable, option is thatthe display is glued directly on the transparent portion of the bodywith an anisotropic conductive adhesive. This adhesive is subsequentlycured using ultraviolet radiation. The adhesive can be applied as alaminated film. The preferred alternative is that a paste withconductive particles is dispensed on the body with the conductors. Thisis then exposed to ultraviolet radiation which passes through the body,or through a portion of the display. It is an advantage of this methodof assembly that the number of contacts made can be very large and thatthe pitch can be small. It thus becomes possible that the display driverintegrated circuit is embedded in the body. This reduces the amount ofassembly steps, compared to the alternative where the driver integratedcircuit is assembled to the display.

In a second embodiment, the light path is present between the opticalelement and an opto-electrical element or electro-optical element thatis also embedded in the body and is electrically connected to thepattern of conductors. Applications hereof include embodiments in whichthe display and the image sensor are also integrated in the body.However, there is a further range of applications in the sphere ofoptical transmission of data. A first application is the combination ofa laser diode and a photodiode in a dual-wavelength optical transceivermodule. This application is known per se from EP-A 733288. Anotherapplication is the optical communication between two semiconductorelements. This application has been described in the non-prepublishedapplication EP02079915.1 (PHNL021172). It is preferred that the body isprovided with attachment means for attachment of external components andan optical fiber in particular. A good attachment of an optical fiber toa photodiode is very important for an adequate transmission of opticalsignals from the fiber to the photodiode. This turns out to be alimiting factor in the integration of photodiodes in various modules.The three-dimensional shape allows however a good and neverthelesssimplified attachment. First of all, a V-shaped groove can be presentfor the optical fiber. Then clamping or other suitable attachmentmeans—such as those based on complementary shapes—can be used to enablethat the end of the fiber is aligned well with the photodiode.

In a third embodiment, the light path is present between the opticalelement and a surface area of the body, and a further electrical elementis electrically connected to the pattern of conductors, the pattern ofconductors comprising an interconnect between the further electricalelement and the optical element. In this embodiment, the elements aremutually connected electrically only. Applications of this embodimentinclude systems in which the optical element is a photosensitive sensor,whereas the further element is electro-optical, such as a light-emittingdiode or a display. The output of the sensor is thus used as an inputfor the further element. Further included are systems in which theoptical element is used for the reception of energy and optionallysignals, and the further element uses the energy and processes thesignals. An example is an integrated circuit integrated in an opticaldisc or card, that is provided with a photodiode for power and datatransmission. In another example the optical element is a solar cell andthe further element a microprocessor, the body as a whole being a clockor a radio or the like and further being provided with all necessaryfeatures and possibly a rechargeable battery to be loaded with theenergy from the solar cell. The advantage of this implementation istwofold: first, the body may have the shape of the desired product.Secondly, the pattern of conductors can be designed so as to minimizeelectrical losses.

Regarding the elaboration of the conductors in the body, the followingis observed:

the first portion in the body of the invention may be as large as thecomplete body. The minimal size originates from the requirement of thecontinuous light path. The first portion may be limited to a certainarea in that the body is provided in a process wherein more than onemolding operation is performed, for instance with the help of a moldwith two chambers. The first portion may be limited in all directions;an example is that the transparent first portion is completely or nearlycompletely overmolded with a non-transparent plastic.

The pattern of conductors is provided within the body with the aid of asacrificial layer that is removed after the molding operation. However,there are several tricks through which the pattern of conductors can bepartly or completely embedded in the body. First of all, a furthermolding or coating step might be carried out after removal of thesacrificial layer. Secondly, the sacrificial layer may be substantiallyremoved in a first area before the molding step, without damaging thepattern of the conductors. The conductors will then be provided insidethe body within the first area. The removal of the sacrificial layer canbe realized by cutting, thereby separating the individual conductors.Part of the sacrificial layer, may and will be maintained and embeddedwith the conductors into the body. Thirdly, it is possible to useunderetching of the pattern of conductors in combination with conductorsof different width. The space created by the underetching will be filledby the material of the body. The pattern of conductors may further befolded prior to inclusion in the body, so as to provide it along a firstand a second face of the body, or even to contact devices present atopposed sides.

The laterally displaced connection means will be used for contactingcarriers, connectors or components. Examples of connection means includecontact pads or regions for galvanic coupling, antennas for wirelessconnection and capacitor plates for capacitive coupling. In case aconnector is used, it is preferably secured to the body by overmolding;it is positioned on the pattern of conductors before the provision ofthe body, but is not completely embedded in the body. In case a flexfoil connection is desired, this flex foil can be integrated into thebody by providing the body with a portion of an elastic material.

In a preferred embodiment, the conductors are anchored mechanically inthe body. The mechanical anchoring is realized in that the conductorsare not block-shaped prior to the molding step, but have another shape.In a first example the conductor extends into the sacrificial layer, inwhich layer it has a reduced diameter. This is realized by underetching.In a second example the conductor is provided with the shape of amushroom. This is realized by electroplating the conductors to theextent that the conductors extend above the resist used to provide thedesired pattern. In a third example, the conductors are basicallythree-layered stacks, with the middle layer having a different diameter(particularly smaller) than the upper and lower layer. This differencein diameter is for instance realized with selective etching of thematerial of the middle layer as compared to the other layers.

It is furthermore preferred, particularly in case the material ormaterials of the body are provided by means of insert molding, to useadditional coatings for improved adhesion between the metal and thepolymeric material. Such coatings are for instance based on copolymersof alkylacrylates and acrylic acids.

It is furthermore preferred that the body is provided with means formechanical attachment of at least one external component. Such acomponent can be an electrical component, such as a display, an opticalcomponent, such as a lens and a mechanical component such as a casing.The means for mechanical attachment include cavities, through-holes,clamping means, corresponding shapes so as to enable a locker and keymechanism, a screw thread and the like as known per se. Particularlypreferred is a cavity fitted for the external component.

Any further elements besides the optical element may be integrated inthe body and electrically connected to the pattern of conductors. Thesefurther elements can be auxiliary components such as resistors,capacitors, inductors, filters and diodes. However also signalprocessing units such as a display driver integrated circuit can beprovided into the body. The latter sets additional requirements on thepitch of the conductor pattern, which can be met for instance with afoil based on a sacrificial layer of Al and a conductor pattern of Cu,which pattern is mechanically anchored into the body.

These and other aspects of the body and the device of the invention willbe further explained with reference to the Figures, in which:

FIG. 1 shows a perspective, diagrammatic and exploded view of a priorart device;

FIG. 2 shows a perspective, diagrammatic and exploded view of a deviceof the invention;

FIG. 3 shows a perspective, diagrammatic view of the foil withcomponents before molding;

FIG. 4 shows a diagrammatic top view of the layout of the pattern ofconductors;

FIG. 5 shows a perspective, diagrammatic view of the body;

FIG. 6 shows a diagrammatic cross-sectional view of a part of the deviceof the invention, and

FIGS. 7-11 show perspective, diagrammatic views of a second embodimentof the foil, the body and the device of the invention.

The Figures are not (completely) drawn to scale and equal referencenumbers in different Figures refer to similar parts.

FIG. 2 shows a perspective, diagrammatic and exploded view of a deviceof the invention. The device comprises a body 10 having athree-dimensional shape that is derived from its application. In thiscase, the body is shaped to be suitable as mechanical support for allcomponents at the user interface side in a mobile phone. To this end,holes 18 and clamping means 19 for mechanical attachment of theloudspeaker 30, the casing 40 and non-shown buttons are present. Apattern of conductors 15 is present at a surface of the body 10.Light-emitting diodes 12, a display driver integrated circuit 22 andother elements 16 are embedded in the body 10 and electrically connectedto at least some of the conductors of the pattern 15. Attached to thebody 10 is the display 20, through a double sided tape 21, and aloudspeaker 40. The body 10 is covered by a casing 40 for estheticreasons.

FIGS. 3 and 5 show two stages in the manufacture of the body 10 of theinvention. In a first step, a foil 50 is provided comprising asacrificial layer 51 and the pattern of conductors 15, that is not shownspecifically in FIG. 3, but in FIG. 4. In this example, the foil 50comprises a sacrificial layer 51 of Al and conductors of Cu. A layer ofNiAu is provided on top of the conductors 15 so as to improve thesolderability. The foil in this example is prepared using an etchingstep and a cutting step. In the etching step, first the copper layer isetched into the pattern of conductors 15, for instance withferrichloride. Thereafter the etching is continued into the aluminum tocreate the required underetching. Aluminum can be etched selectivelywith respect to copper using a solution of sodium hydroxide. In thecutting step, the sacrificial layer 51 is partly cut away, so that theoverall outline fits into the desired shape of the body. The lightemitting diodes 12, the display driver integrated circuit 22 and otherelements 16, in this case surface mountable resistors and capacitors,are provided. In addition, a connector 13 is provided. The connector 13is provided with hooks at the end at which it is attached to the patternof conductors, to ensure fixation after the overmolding operation.

FIG. 4 shows a diagrammatic top view in which the layout of the patternof conductors 15 is shown. As is clear from this Figure, there are twolight-emitting diodes 12, that are positioned at a mutual angle of about22°. After provision of the body, the emitted light will go into thebody directly and will uniformly and completely illuminate the part ofthe body present under the display 20. It is an advantage of theembedding in question that use can be made of light-emitting diodeswithout a package and without a lens for focusing purposes. However,packaged light-emitting diodes can be used as well. As is furthermoreclear from this Figure, the contact pads 14 for contacting the connectorare laterally displaced with respect to the optical elements, i.e. thelight-emitting diodes 12, and also with respect to the display driverintegrated circuit 22. The contact pads 14 have a diameter which islarger than that of the rest of the pattern 15.

FIG. 5 shows a perspective, diagrammatic view of the body. This body isprovided by insert molding of polycarbonate, in a manner known to theskilled person. Afterwards, the sacrificial layer 51 is removed byetching, and the fingers of the connector 13 are bent. The body is nowready for use and integration into the device 100. The display 20 andthe loudspeaker 30 can be attached at the side at which the pattern ofconductors 15 is present at the surface.

FIG. 6 shows a diagrammatic cross-sectional view of a part of the deviceof the invention. This clarifies the attachment of the display 20 to thebody 10. Although not shown here, it is preferred that the body 10extends so as to act as mechanical support for the display 20. Thedisplay 20 and the body 10 are attached to one another with ananisotropically conducting adhesive 29, that is provided at selectedregions of the surface of the body 10. To this end, the display 20 isprovided with an edge 28, made of glass, at a surface of whichtransparent conductors, in this example of indium tin oxide (ITO) arepresent. The adhesive 29 is cured either through the glass edge 28 ofthe display 20 or through the body 10.

FIG. 7-11 show perspective diagrammatic views of a second embodiment ofthe invention. A first difference with the first embodiment is that thedisplay driver 22 is not integrated in the body, but attached to thedisplay 20. Another difference is that the other elements 16 and theconnectors 13 are encapsulated in a specific encapsulation 60. By virtuethereof, further freedom is achieved in the choice of the encapsulant,so as to provide additional chemical resistance and mechanical strength.Additionally, this encapsulation 60 is provided with cavities 61,62 soas to improve the mechanical adhesion. A further difference is that thefoil 50 is bent at its edge 52. This improves the connection to thedisplay.

FIG. 7 shows the foil 50 with the elements 12,16 and the connectors 13.The pattern of conductors 15 is shown partially, and additionalthrough-holes 53,54 are provided, so-called pilot holes. At this stagethe foil 50 is bent, so as to create the edge 52.

FIG. 8 shows the foil 50 after the other elements 16 and the connector13 is partially overmolded. Use is made of the molding materialpolyphenylenesulfide (PPS). However, other engineering plastics can beused alternatively. The created encapsulation 60 is provided withcavities 61,62 for improved mechanical attachment and is given a shapesuch that it is not present in (?) the light path.

FIG. 9 shows the body 10 that has been formed by application of a secondmolding material. It is provided with through-holes 18 and cavities formechanical attachment. A transparent material is used as the secondmolding material, in this case polycarbonate, and the light-emittingdiodes 12 are encapsulated therein. The attachment of the polycarbonateto the PPS may be improved by subjecting the PPS first to a surfacetreatment, by an adequate choice of the mold of the PPS so as to provideit with a mechanically rough surface, by carrying out a heat treatmentwhich will lead to adhesion between both molding materials, etc.

FIG. 10 shows the body 10 from the opposite side in comparison with FIG.9, and after the sacrificial base layer 51 has been removed by etching.The conductors that connect the other elements 16, the diodes 12 and theconnector springs 13 are exposed at the surface (although not shown).

FIG. 11 shows the resulting device 100, after the display 20 with thedisplay driver IC 22 attached to it, is provided on the body 10. Thediodes 12 now shine in the light path through the body 10, which resultsin backlighting of the display 20. In order to optimize such light guidebehavior, the body 10 is provided with adequate surface structures.

1. A one-piece body of electrically insulating material having athree-dimensional shape derived from its intended function said bodydefining a plane having a longitudinal and a lateral and a perpendiculardirections, said body being molded in one piece and provided with apattern of electrical conductors extending with said body in the planeof said body, and at least one optical element being integrally formedwith and embedded in said one-piece body, the optical element beingelectrically connected to the pattern of conductors, the pattern ofconductors being provided with electrical connection means that arelaterally displaced with respect to the optical element, and saidone-piece body comprising a first portion with a transparent,electrically insulating material constituting a light path to theoptical element, wherein the light path is present between the opticalelement and one of an opto-electrical element and an electro-opticalelement that is also embedded in the one-piece body and is electricallyconnected to the pattern of conductors.
 2. The one-piece body as claimedin claim 1, wherein the light path is present between the opticalelement and a surface area of the one-piece body suitable for assemblyof an opto-electrical or electro-optical element.
 3. The one-piece bodyas claimed in claim 1, wherein: the light path is present between theoptical element and a surface area of the one-piece body, a secondelectrical element is electrically connected to the pattern ofconductors, the pattern of conductors comprising an interconnect betweenthe second electrical element and the optical element.
 4. The one-piecebody as claimed in claim 3, wherein a selected one of the opticalelement and the second electrical element is a light sensitive elementand the non-selected element is an electro-optical element, a secondlight path being present between the second element and a surface areaof the one-piece body.
 5. The one-piece body as claimed in claim 1,wherein the pattern of conductors is provided at least partially at asurface of the one-piece body and is provided with contact pads forestablishing electric contact to an element that is to be assembled atthe surface of the one-piece body.
 6. The one-piece body as claimed inclaim 5, wherein the conductors are mechanically anchored in theone-piece body.
 7. The one-piece body as claimed in claim 1, wherein theone-piece body has a three-dimensional shape that comprises means formechanical attachment of at least one external component to theone-piece body.
 8. The one-piece body as claimed in claim 7, wherein themeans include a cavity fitted for the external component.
 9. Anelectronic device comprising a one-piece body of electrically insulatingmaterial having a three-dimensional shape derived from its intendedfunction said body defining a plane having a longitudinal and a lateraland a perpendicular directions, said body being molded in one piece andprovided with a pattern of electrical conductors extending with saidbody in the plane of said body, and at least one optical element beingintegrally formed with and embedded in said one-piece body, the opticalelement being electrically connected to the pattern of conductors, thepattern of conductors being provided with electrical connection meansthat are laterally displaced with respect to the optical element, andsaid one-piece body comprising a first portion with a transparent,electrically insulating material constituting a light path to theoptical element and at least one of an opto-electrical and anelectro-optical element attached to the surface of the one-piece body,wherein the embedded optical element is a light-emitting diode and theelectro-optical element is a display, and wherein the light-emittingdiode is used as backlight for the display, the light path being presentin between the light-emitting diode and the display.
 10. The one-piecebody as claimed in claim 1, wherein the one-piece body is molded as amechanical support for a display.
 11. The one-piece body as claimed inclaim 1, wherein all of the one-piece body is transparent.
 12. Theone-piece body as claimed in claim 1, wherein the one-piece bodycomprises a flexible portion at an edge of the one-piece body.